1. Field of the Invention
This invention pertains to earthmovers, to excavators, and in particular to a fluid- or hydraulic-actuated excavator of the front-loading, level-crowding variety. More particularly the invention concerns improvements in the linkage for the actuation and control of a bucket in such a fluid-actuated excavator.
2. Description of the Prior Art
The implement assembly of a front-loading hydraulic excavator, mounted on a full-revolving carrier of the track or wheel type, normally comprises a boom pivoted at one end on the vehicle, a stick pivotally connected at one end to the outer or front end of the boom, and a front-loading or front-opening bucket pivotally mounted on the other end of the stick. A hydraulic cylinder or cylinders under operator control are provided for operation of each of the boom, the stick, and the bucket.
As is well known, the boom, stick, bucket, and bucket control cylinders of the above implement assembly form in combination a parallelogram-type linkage. The geometry of this linkage permits the bucket to crowd forward parallel to the ground without requiring manipulation of the hoist or bucket angle.
The known parallelogram-type linkage has problems, however, arising from the fact that the joints forming the four corners of the parallelogram are fixed, not displaceable or adjustable with respect to each other. Thus, once the bucket is set for a certain operating attitude or angle, this angle remains substantially unchanged if the stick is pivoted relative to the boom. A change from one bucket attitude to another is possible only through the actuation of the bucket control cylinders.
The operation of a front-loading hydraulic excavator will be relieved of much of his fatigue if the bucket can be set for a desired one of several operating attitudes without manipulation of the bucket control cylinders. It is also desired that the bucket be conditioned for two successive, different attitudes (e.g., a crowd attitude followed by a carry or a dump attitude) at one time.
Another problem with the conventional parallelogram-type linkage is that the angle of the bucket relative to the ground increases as the boom is raised. The consequent spilling of the load over the back of the bucket can be avoided only by manually maintaining the bucket in the proper carry attitude throughout its upward stroke. This also adds to the operator's work and fatigue.